This study will investigate the development of topography and connectivity of primary somatosensory (S1) and motor (M1) cortices o determine how the organization of these areas is altered during the dramatic changes in body morphology and sensory experiences during the first few postnatal weeks. These issues will be investigated in developing Long-Evans rats as postnatal days (P) 5, 10, 15, 20, and during adulthood (>P60). Experiment 1 will investigate the development of somatotopic maps within S1. The boundaries of S1 will be electrophysiologically determined using multi-unit recording techniques. The area of the cortical sheet dedicated to different body representations (including the head/vibrissae, trunk, forelimbs, and hindlimbs) will be calculated at each age, and compared across ages, to determine how the functional organization of S1 changes across development. Experiment 2 will investigate the development of neuroanatomical connections within and between S1 and M1 was well as the thalamus and spinal cord. PUBLIC HEALTH RELEVANCE: Recently there has been tremendous progress in the treatment of traumatic brain injuries. Some of this research has demonstrated that the healing process is remarkably similar to the developmental process. Specifically, both of these processes involve neurochemical changes, the release of neural growth factors and subsequent neuronal growth, and the formation of novel connections within the brain. A greater understanding of the developmental process could provide insight into how the brain recovers following stroke or other traumatic brain injury. The studies proposed here will increase our understanding of how brain organization, and specifically somatotopy within major sensory areas, develops. This information may then be used to develop novel approaches to the diagnosis and treatment of traumatic brain injury and other neurological disorders.